Molecular Regulation of Photoreceptor Cell Death

摘要 视网膜疾病是导致失明的主要原因，对患者和社会产生巨大影响。根 视力不佳的原因是感光细胞的死亡，这主要是由于正常细胞的破坏。 这些细胞和下面的视网膜色素上皮（RPE）之间的稳态相互作用。保存 光感受器（PR）的生存力和功能仍然是一个关键的未满足的医疗需求。PR的含氧量最高 体内的消耗。脉络膜脉管系统通过RPE供应这种需求-这一过程 需要紧密的并列和亲密的互动。视网膜-RPE稳态破坏的时期可能是 预期导致显著和快速的PR细胞死亡。然而，PRs可以在RPE降低的时期存活下来， 营养支持，导致治疗视网膜疾病的临床机会窗口。目前有 没有治疗选择来维持PR活力或减缓细胞死亡速率以延长该治疗窗。在 实验性视网膜脱离（RD）是一种有效的PR-RPE稳态改变模型，我们发现 激活促生存和死亡途径。前者的例子包括释放保护性 细胞死亡主要通过Fas介导的细胞凋亡发生。一 我们知识上的一个主要空白是我们不知道这些细胞保护和 细胞破坏途径。我们假设HMGB 1和小胶质细胞代表了关键的内在和外在的， 影响力，分别。我们的初步数据有力地指出了已知的多功能蛋白质的作用。 作为高迁移率族蛋白1（HMGB 1）在PR的内在保护和先天免疫应答中的作用， 在具体目标1中，我们将定义HMGB 1在PR死亡和视网膜小胶质细胞活化中的作用 在RD后和遗传性视网膜变性模型中。我们的初步数据表明， 视杆细胞PR中的HMGB 1对保护性自噬和RD后小胶质细胞的激活的作用。我们将调查 胞浆HMGB 1在细胞自主激活和促存活通路稳定中的功能 PRs和释放的HMGB 1促进小胶质细胞活化的功能。在具体目标2中，我们将确定 小胶质细胞在RD后炎症反应和PR死亡中的作用。的相对贡献 小胶质细胞和浸润性髓系白细胞以及免疫应答如何影响PR存活尚不清楚。 基于我们的初步数据，我们假设常驻小胶质细胞是RD的主要第一反应者， 并且小胶质细胞最初是保护性的，但最终转变为有害的炎性表型。我们 进一步假设p38 a-ULK 1轴有助于这种转变。我们将定义和描述 免疫细胞响应RD和测试是否靶向p38 a和促进自噬是保护性的， Rd.在这项赠款中提出的工作将提供一个重要的理解机制， 控制感光细胞的存活。只有通过对这些基本过程的描述， 将能够开发靶向疗法，以保持这些细胞的存活并改善患者的治疗效果。

ABSTRACT Retinal diseases are a leading cause of blindness, tremendously impacting patients and society. A root cause of poor vision is death of the photoreceptor cell, which primarily results from disruption of the normal homeostatic interaction between these cells and the underlying retinal pigment epithelium (RPE). Preserving photoreceptor (PR) viability and function remains a critical unmet medical need. PRs have the highest oxygen consumption in the body. The choroidal vasculature supplies this demand through the RPE – a process that requires close apposition and intimate interaction. Periods of disrupted retina-RPE homeostasis might be expected to result in marked and rapid PR cell death. However, PRs can survive periods of reduced RPE nutritional support, resulting in a clinical window of opportunity for treating retinal disease. Currently there are no therapeutic options to maintain PR viability or slow the rate of cell death to extend this treatment window. In experimental retinal detachments (RD), a validated model of altered PR-RPE homeostasis, we have found activation of both pro-survival and death pathways. Examples of the former include the release of protective cytokines and activation of autophagy; whereas cell death occurs primarily through Fas-mediated apoptosis. A major gap in our knowledge is that we do not know the upstream activators of these cytoprotective and cytodestructive pathways. We hypothesize that HMGB1 and microglia represent key intrinsic and extrinsic influences, respectively. Our preliminary data strongly point towards a role for the multifunction protein known as High-Mobility Group Box 1 (HMGB1) in the intrinsic protection of PR and the innate immune response to stressed PR. In Specific Aim 1 we will define the role of HMGB1 in PR death and activation of retinal microglia after RD and in a model of inherited retinal degeneration. Our preliminary data connects the upregulation of HMGB1 in rod PR to protective autophagy and the activation of microglia following RD. We will investigate the function of cytosolic HMGB1 in cell-autonomous activation and stabilization of pro-survival pathways within PRs and the function of released HMGB1 to promote microglial activation. In Specific Aim 2 we will determine the role of microglia in the inflammatory response and PR death following RD. The relative contributions of microglia and infiltrating myeloid leukocytes and how the immune response affects PR survival are not clear. Based on our preliminary data, we hypothesize that resident microglia are the major first responders to RD, and that microglia are initially protective but eventually shift to a detrimental inflammatory phenotype. We further hypothesize that the p38a-ULK1 axis contributes to this shift. We will define and characterize the immune cells responding to RD and test if targeting p38a and promoting autophagy are protective following RD. The work proposed in this grant will provide a critical understanding of the mechanisms regulating the control of photoreceptor cell survival. It is only through the delineation of these fundamental processes that we will be able to develop targeted therapies to keep these cells alive and improve patient outcomes.